Your so called biodegradable plastic bag might not actually biodegrade

At this point, images of plastic waste-filled landscapes have managed to reach and horrify much of the general public. Plastic bag bans are proliferating in response. Now, bags made from alternative, biodegradable plastics are popping up in retail stores with regularity. But will those plastics actually biodegrade?

It seems that they might not, or at least not as quickly as people might think. For one thing, they often need very specific conditions to degrade at all. For example, most products labeled as “compostable plastic” degrade only in special heat-treated industrial composting facilities. They can’t degrade in a backyard compost pile, and they can’t be recycled, because they would contaminate the recycling stream. So if the community that is using compostable plastic doesn’t have an industrial composting facility, that object is going straight to the landfill, where it will probably last a very, very long time.

Now, a new paper is casting doubt on several types of “biodegradable” plastics. The paper, published April 28 in Environmental Science & Technology, found that three types of so-called biodegradable plastic bags didn’t degrade after three years in the environment. The team of researchers from the University of Plymouth in the UK tested compostable, biodegradable, and oxo-biodegradable plastic bags, which are often marketed with statements indicating they can be “recycled back into nature much more quickly than ordinary plastic” or that they are “plant-based alternatives to plastic.” (Oxo-biodegradable plastics are meant to be able to degrade by way of exposure to heat or light, which is seen as an advantage over other degradable plastics, which only break down due to exposure to microbes.)

This bag was labeled as “biodegradable.” It seems to be doing just fine after three years in seawater.

The team subjected the bags to three conditions: They buried them in soil, left them outdoors to be exposed to the sun and weather, and submerged them in seawater for three years.

At the end of the three years, the only bag that fully disappeared was the compostable plastic bag submerged in seawater. The compostable bag buried in soil remained intact after three years, though it could no longer hold weight without tearing. All three bags left in the open air degraded into scraps, but did not disappear, which raised questions for the researchers about whether biodegradable bags could be contributing the the global microplastics problem.

Perhaps most surprising was that both the “biodegradable” and “oxo-biodegradable” bags could still hold a full load of shopping after three years in the marine environment or buried in soil (the researchers loaded them with 5 lbs, or 2.25 kg, worth of objects).

In both cases, the bags were presumably exposed to naturally occurring microbes, but they weren’t broken down. It is unclear how long it may have taken—or if the rate of breakdown would have been faster than that of a conventional plastic bag.

It’s clear that none of these bags, with perhaps the exception of the compostable bag left at sea, are meaningfully solving the plastic pollution problem in the immediate future—at least not within three years. Of course, conventional plastic can last hundreds or perhaps thousands of years in the environment, so from that perspective, three years isn’t very long. But it is unclear how long it might take, and what if any standards are governing the labelling of bags that consumers are almost definitely expecting will not contribute to the global plastic pollution problem.

The eco-plastics industry is still in its infancy. In the US, the Federal Trade Commission puts out guidelines to try to hold the industry to some standards for when it can call itself “degradable.” The FTC writes:

It is deceptive to make an unqualified degradable claim for items entering the solid waste stream if the items do not completely decompose within one year after customary disposal.

Unqualified degradable claims for items that are customarily disposed in landfills, incinerators, and recycling facilities are deceptive because these locations do not present conditions in which complete decomposition will occur within one year.

Biodegradable plastic is a great idea in theory. For now, avoiding buying new plastic—biodegradable or not—might be the more prudent choice.

Featured image: This supposedly biodegradable plastic bag was submerged in seawater for three years.

By Zoë Schlanger, Quartz,

We are drowning in plastic – how much and how did we get there

WE MADE PLASTIC. WE DEPEND ON IT. AND NOW WE’RE DROWNING IN IT.  The miracle material has made modern life possible. But more than 40 percent of plastic is used just once, and it’s choking our waterways.

… Because plastic wasn’t invented until the late 19th century, and production really only took off around 1950, we have a mere 9.2 billion tons of the stuff to deal with. Of that, more than 6.9 billion tons have become waste. And of that waste, a staggering 6.3 billion tons never made it to a recycling bin—a figure that stunned the scientists who crunched the numbers in 2017.
No one knows how much unrecycled plastic waste ends up in the ocean, Earth’s last sink. In 2015, Jenna Jambeck, a University of Georgia engineering professor, caught everyone’s attention with a rough estimate: between 5.3 million and 14 million tons each year just from coastal regions. Most of it isn’t thrown off ships, she and her colleagues say, but is dumped carelessly on land or in rivers, mostly in Asia. It’s then blown or washed into the sea. Imagine five plastic grocery bags stuffed with plastic trash, Jambeck says, sitting on every foot of coastline around the world—that would correspond to about 8.8 million tons, her middle-of-the-road estimate of what the ocean gets from us annually. It’s unclear how long it will take for that plastic to completely biodegrade into its constituent molecules. Estimates range from 450 years to never.
… And yet there’s a key difference: Ocean plastic is not as complicated as climate change. There are no ocean trash deniers, at least so far. To do something about it, we don’t have to remake our planet’s entire energy system.

“This isn’t a problem where we don’t know what the solution is,” says Ted Siegler, a Vermont resource economist who has spent more than 25 years working with developing nations on garbage. “We know how to pick up garbage. Anyone can do it. We know how to dispose of it. We know how to recycle.” It’s a matter of building the necessary institutions and systems, he says—ideally before the ocean turns, irretrievably and for centuries to come, into a thin soup of plastic.


In Plymouth, under the gray gloom of an English autumn, Richard Thompson waited in a yellow slicker outside Plymouth University’s Coxside Marine Station, at the edge of the harbor. A lean man of 54, with a smooth pate rimmed with gray hair, Thompson was headed for an ordinary career as a marine ecologist in 1993—he was working on a Ph.D. on limpets and microalgae that grow on coastal rocks—when he participated in his first beach cleanup, on the Isle of Man. While other volunteers zoomed in on the plastic bottles and bags and nets, Thompson focused on the small stuff, the tiny particles that lay underfoot, ignored, at the high tide line. At first he wasn’t even sure they were plastic. He had to consult forensic chemists to confirm it.

There was a real mystery to be solved back then, at least in academic circles: Scientists wondered why they weren’t finding even more plastic in the sea. World production has increased exponentially—from 2.3 million tons in 1950, it grew to 162 million in 1993 and to 448 million by 2015—but the amount of plastic drifting on the ocean and washing up on beaches, alarming as it was, didn’t seem to be rising as fast. “That begs the question: Where is it?” Thompson said. “We can’t establish harm to the environment unless we know where it is.”

In the years since his first beach cleanup, Thompson has helped provide the beginnings of an answer: The missing plastic is getting broken into pieces so small they’re hard to see. In a 2004 paper, Thompson coined the term “microplastics” for these small bits, predicting—accurately, as it turned out—that they had “potential for large-scale accumulation” in the ocean.

When we met in Plymouth last fall, Thompson and two of his students had just completed a study that indicated it’s not just waves and sunlight that break down plastic. In lab tests, they’d watched amphipods of the species Orchestia gammarellus—tiny shrimplike crustaceans that are common in European coastal waters—devour pieces of plastic bags and determined they could shred a single bag into 1.75 million microscopic fragments. The little creatures chewed through plastic especially fast, Thompson’s team found, when it was coated with the microbial slime that is their normal food. They spat out or eventually excreted the plastic bits.

Microplastics have been found everywhere in the ocean that people have looked, from sediments on the deepest seafloor to ice floating in the Arctic—which, as it melts over the next decade, could release more than a trillion bits of plastic into the water, according to one estimate. On some beaches on the Big Island of Hawaii, as much as 15 percent of the sand is actually grains of microplastic. Kamilo Point Beach, the one I walked on, catches plastic from the North Pacific gyre, the trashiest of five swirling current systems that transport garbage around the ocean basins and concentrate it in great patches. At Kamilo Point the beach is piled with laundry baskets, bottles, and containers with labels in Chinese, Japanese, Korean, English, and occasionally, Russian. On Henderson Island, an uninhabited coral island in the South Pacific, researchers have found an astonishing volume of plastic from South America, Asia, New Zealand, Russia, and as far away as Scotland.

As Thompson and I talked about all this, a day boat called the Dolphin was carrying us through a light chop in the Sound, off Plymouth. Thompson reeled out a fine-mesh net called a manta trawl, usually used for studying plankton. We were close to the spot where, a few years earlier, other researchers had collected 504 fish of 10 species and given them to Thompson. Dissecting the fish, he was surprised to find microplastics in the guts of more than one-third of them. The finding made international headlines.

In Life magazine in 1955, an American family celebrates the dawn of “Throwaway Living,” thanks in part to disposable plastics. Single-use plastics have brought great convenience to people around the world, but they also make up a big part of the plastic waste that’s now choking our oceans.



After we’d steamed along for a while, Thompson reeled the manta trawl back in. There was a smattering of colored plastic confetti at the bottom. Thompson himself doesn’t worry much about microplastics in his fish and chips—there’s little evidence yet that they pass from the gut of a fish into the flesh we actually eat. (See We Know Plastic Is Harming Marine Life. What About Us?) He worries more about the things that none of us can see—the chemicals added to plastics to give them desirable properties, such as malleability, and the even tinier nanoplastics that microplastics presumably degrade into. Those might pass into the tissues of fish and humans.

“We do know the concentrations of chemicals at the time of manufacture in some cases are very high,” Thompson said. “We don’t know how much additive is left in the plastic by the time it becomes bite-size to a fish.

“Nobody has found nanoparticles in the environment—they’re below the level of detection for analytical equipment. People think they are out there. They have the potential to be sequestered in tissue, and that could be a game changer.”

Thompson is careful not to get ahead of the science on his subject. He’s far from an alarmist—but he’s also convinced that plastic trash in the ocean is far more than an aesthetic problem. “I don’t think we should be waiting for a key finding of whether or not fish are hazardous to eat,” he said. “We have enough evidence to act.”

In one of their early applications, they saved wildlife. In the mid-1800s, piano keys, billiard balls, combs, and all manner of trinkets were made of a scarce natural material: elephant ivory. With the elephant population at risk and ivory expensive and scarce, a billiards company in New York City offered a $10,000 reward to anyone who could come up with an alternative.

As Susan Freinkel tells the tale in her book, Plastic: A Toxic Love Story, an amateur inventor named John Wesley Hyatt took up the challenge. His new material, celluloid, was made of cellulose, the polymer found in all plants. Hyatt’s company boasted that it would eliminate the need “to ransack the Earth in pursuit of substances which are constantly growing scarcer.” Besides sparing at least some elephants, celluloid also helped change billiards from solely an aristocratic pastime to one that working people play in bars.

That’s a trivial example of a profound revolution ushered in by plastic—an era of material abundance. The revolution accelerated in the early 20th century, once plastics began to be made from the same stuff that was giving us abundant, cheap energy: petroleum. Oil companies had waste gases like ethylene coming out the stacks of their refineries. Chemists discovered they could use those gases as building blocks, or monomers, to create all sorts of novel polymers—polyethylene terephthalate, for example, or PET—instead of working only with polymers that already existed in nature. A world of possibilities opened up. Anything and everything could be made of plastic, and so it was, because plastics were cheap.

They were so cheap, we began to make things we never intended to keep. In 1955 Life magazine celebrated the liberation of the American housewife from drudgery. Under the headline “Throwaway Living,” a photograph showed a family flinging plates, cups, and cutlery into the air. The items would take 40 hours to clean, the text noted—“except that no housewife need bother.” When did plastics start to show their dark side? You might say it was when the junk in that photo hit the ground.

Six decades later, roughly 40 percent of the now more than 448 million tons of plastic produced every year is disposable, much of it used as packaging intended to be discarded within minutes after purchase. Production has grown at such a breakneck pace that virtually half the plastic ever manufactured has been made in the past 15 years. Last year the Coca-Cola Company, perhaps the world’s largest producer of plastic bottles, acknowledged for the first time just how many it makes: 128 billion a year. Nestlé, PepsiCo, and others also churn out torrents of bottles.

The growth of plastic production has far outstripped the ability of waste management to keep up: That’s why the oceans are under assault. “It’s not surprising that we broke the system,” Jambeck says. “That kind of increase would break any system not prepared for it.” In 2013 a group of scientists issued a new assessment of throwaway living. Writing in Nature magazine, they declared that disposable plastic should be classified, not as a housewife’s friend, but as a hazardous material.

In recent years the surge in production has been driven largely by the expanded use of disposable plastic packaging in the growing economies of Asia—where garbage collection systems may be underdeveloped or nonexistent. In 2010, according to an estimate by Jambeck, half the world’s mismanaged plastic waste was generated by just five Asian countries: China, Indonesia, the Philippines, Vietnam, and Sri Lanka.

“Let’s say you recycle 100 percent in all of North America and Europe,” says Ramani Narayan, a chemical engineering professor at Michigan State University who also works in his native India. “You still would not make a dent on the plastics released into the oceans. If you want to do something about this, you have to go there, to these countries, and deal with the mismanaged waste.”

A LIFETIME OF PLASTIC: The first plastics made from fossil fuels are just over a century old. They came into widespread use after World War II and are found today in everything from cars to medical devices to food packaging. Their useful lifetime varies. Once disposed of, they break down into smaller fragments that linger for centuries.

Total: 448 million tons produced in 2015

Growth in Asia: As the economies in Asia grow, so does demand for consumer products—and plastics. Half the world’s plastics are made there, 29 percent in China.

The legacy of World War II: Shortages of natural materials during the war led to a search for synthetic alternatives—and to an exponential surge in plastic production that continues today.  The largest market for plastics today is for packaging materials. That trash now accounts for nearly half of all plastic waste generated globally; most of it never gets recycled or incinerated.

DURABLE CHAINS: Plastics are polymers: Long-chain molecules made of repeating links, or monomers. The chains are strong, light, and durable, which makes them so useful—and so problematic when they’re disposed of carelessly. Chemical reactions Heat, pressure, and catalysts drive reactions that link the monomers. The monomers that are synthesized into plastics are usually derived from fossil fuels such as crude oil and natural gas.

END PRODUCTS: PET is one of the most widely used polymers. Methanol, a by-product of PET synthesis, is typically incinerated.
By Laura Parker, National Geographic
June 2018